Field of the Invention
The invention relates to a radar apparatus for deriving a target.
Description of the Background Art
Conventionally, a radar apparatus installed in a vehicle transmits a transmission wave from a transmission antenna, receives a reflection wave from a target at a reception antenna, and derives a target location to the vehicle (radar apparatus) or other information. Specifically, the radar apparatus first mixes, to generate a beat signal, a transmission signal corresponding to the transmission wave whose frequency changes in a prescribed cycle, and a reception signal corresponding to the reflection wave. That is, the radar apparatus generates a beat signal based on a difference frequency (beat frequency) between the transmission signal and the reception signal in each of the UP sections in which a frequency increases in a prescribed cycle and DOWN sections in which a frequency decreases in a prescribed cycle.
Next, the radar apparatus generates a signal (conversion signal) for each frequency by performing FFT (Fast Fourier Transform) processing to the beat signal. Then, the radar apparatus extracts, in each of the UP section and the DOWN section, a prescribed number of the signals whose levels are high as peak signals among the conversion signals. After that, the radar apparatus pairs a peak signal in the UP section and a peak signal in the DOWN section based on a prescribed condition to derive pair data.
Next, the radar apparatus determines whether there is a temporally continuous relation between the pair data derived in the previous processing and the pair data derived in the processing this time. In the case where there is a temporally continuous relation between the two sets of the pair data, the radar apparatus derives location information, relative velocity information or other information about a target based on the derived pair data.
Then, the radar apparatus outputs the derived location information, relative velocity information or other information about the target to a vehicle controller, and performs necessary vehicle control in accordance with the target information.
However, in the case where a vehicle is traveling in the environment having a structure of a wall or a ceiling laterally or upward, for example, in a tunnel or on a truss bridge, the radar apparatus receives a lot of reflection waves from the wall or the ceiling, which may cause erroneous pairing. As a result, the erroneous pairing may cause erroneous target derivation, which may degrade detection performance.